This application claims the benefit of Korean Application No. 00-5731 filed Feb. 8, 2000 in the Korean Patent Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to an apparatus for controlling the drive power of a plasma display panel and a method therefor, and more particularly, to a method and apparatus which pre-estimates a load ratio, which is the ratio of the number of discharge cells to be display-discharged to the total number of discharge cells in the plasma display panel, on a frame-by-frame basis, and controls the number of display-discharge pulses in a corresponding frame so that the number of display-discharge pulses in the corresponding frame is inversely proportional to the preestimated load ratio.
2. Description of the Related Art
Since plasma display panels have high power consumption due to their drive characteristics, an apparatus for controlling power consumption depending on the load ratio of a frame to be displayed is greatly required.
Referring to FIG. 1, a driving apparatus of a typical plasma display panel 1 includes a controller 2, an address driver 3, an X driver 4, and a Y driver 5. The controller 2 generates drive control signals SA, SY, and SX according to an incoming video signal. The address driver 3 processes an address signal SA from the controller 2 to generate a display data signal, and then applies the generated display data signal to address electrode lines. The X driver 4 processes an X drive control signal SX from the controller 2 to apply the processed X drive control signal SX to X electrode lines. The Y driver 5 processes a Y drive control signal SY to apply the processed Y drive control signal SY to Y electrode lines.
FIG. 2 shows the internal configuration of the controller 2 in the apparatus of FIG. 1. Referring to FIG. 2, the controller 2 includes a subfield generator 21, a power controller 22, a subfield matrix 23, a frame memory 24, a memory interface 25, a rearranger 26, a timing signal generator 27, XY switches 28, and a memory 29. The subfield generator 21 converts input video data signals red (R), green (G) and blue (B) to gray-scale data signals. The subfield matrix 23 classifies the gray-scale data signals based on the type of gray scales. The memory interface 25 stores the classified data signals from the subfield matrix 23 in the frame memory 24, and inputs frame data from the frame memory 24 into the rearranger 26. The rearranger 26 rearranges the frame data input through the memory interface 25 in such a way as to be well suited to a predetermined driving sequence, and outputs the address signal SA as the result thereof.
The timing signal generator 27 generates a timing signal according to an input horizontal synchronization signal HSYNC, a vertical synchronization signal VSYNC, a clock signal CLK, and a driving sequence permanently stored in the memory 29 such as a programmable read only memory (PROM). The XY switches 28 operate according to the predetermined driving sequence and switch the timing signal from the timing signal generator 27 to output the X drive control signal SX and the Y drive control signal SY.
Here, the power controller 22 processes the input video data signals R, G, and B to preestimate a load ratio, which is the ratio of the number of discharge cells to be display-discharged to the number of discharge cells of the plasma display panel 1, on a frame-by-frame basis, and to input a discharge number control signal APC to the timing signal generator 27. The timing signal generator 27 then controls the number of display-discharge pulses in a corresponding frame in such a way as to be inversely proportional to the preestimated load ratio. The operation principle of the power controller 22 is based on a drive characteristic graph shown in FIG. 3.
The drive characteristic graph of FIG. 3 is obtained as follows. First, a load ratio versus electric power characteristic is obtained while changing the number Ns of display-discharge pulses in a frame. Then, load ratios L4, L3, L2 and L1 are equated to reference electric power values with respect to each of the number Ns of display-discharge pulses in a frame. In this case, a load ratio of 100% is set for the lowest number Ns (=500) of display-discharge pulses in a frame. Based on this principle, the following power control is performed depending on the load ratio, L4, L3, L2 and L1.
The highest number Ns (=2,000) of display-discharge pulses in a frame is applied to the load ratio of 0 through L4. The next highest number Ns (=1,500) of display-discharge pulses in a frame is applied to the load ratio which is greater than L4 and less than or equal to L3. The next highest number Ns (=1,000) of display-discharge pulses in a frames is applied to the load ratio which is greater than L3 and less than or equal to L2. The lowest number (=500) Ns of display-discharge pulses in a frame is applied to the load ratio which is greater than L2. Here, the load ratio L1 denotes a load ratio of 100% where all discharge cells perform display-discharge.
The cross points P1, P2, P3, and P4 of the load ratio corresponding to the electric power are linked together to obtain a drive characteristic curve. The number Ns of display-discharge pulses in a frame and the load ratio can be appropriately selected within a range not deviating from the thus-obtained drive characteristic.
FIG. 4 shows the internal configuration of a conventional power controller. Referring to FIG. 4, the conventional power controller includes a load ratio preestimator 41, a low pass filter (LPF) 42, and a discharge number controller 43. The load ratio preestimator 41 preestimates a load ratio, which is the ratio of the number of discharge cells to be display-discharged to the total number of discharge cells in a plasma display panel, by a frame-by-frame basis. The LPF 42 works such that the level of an output signal from the load ratio preestimator 41 does not rapidly change. The discharge number controller 43 outputs a discharge number control signal APC corresponding to the load ratio signal from the LPF 42.
Here, if a level of an output signal from the load ratio preestimator 41 rapidly changes, for example, if the load ratio drops from 95% to 10%, the number Ns of display-discharge pulses in a frame rapidly changes accordingly by the discharge number controller 43. The LPF serves to prevent an electric shock of a system due to the rapid change. However, since the control of the discharge number controller 43 is always delayed by a predetermined time by the LPF 42, where a quickly moving object is displayed on a screen, power consumption increases at the point where this delay occurs. Thus, a speed of changing the display-discharge number per frame is always continuous. In other words, a transition time for changing the display-discharge number is always continuous according to the prior art. Thus, the control of the discharge number controller is inaccurate during the transition time. Where a quickly moving object is displayed, the average range for changing the display discharge number is relatively increased, so that the control of the discharge number controller is more inaccurate during the transition time. Thereby, according to the prior art, power consumption in a plasma display panel can increase more during the transition time.
To solve the above problems, it is an object of the present invention to provide an apparatus which controls the drive power of a plasma display panel that maintains constant power consumption without imposing electrical shock on a system.
It is also an object of the present invention to provide a method of controlling the drive power of a plasma display panel that maintains constant power consumption without imposing electrical shock on a system.
Additional objects and advantages of the invention will be set forth in part in the description which follows, and, in part, will be obvious from the description, or may be learned by practice of the invention.
Accordingly, to achieve the above and other objects, the present invention provides a method of controlling drive power of a plasma display panel by preestimating a load ratio, which is the ratio of the number of discharge cells to be display-discharged to the total number of discharge cells in the plasma display panel, on a frame-by-frame basis and controlling the number of display-discharge pulses in a corresponding frame so as to be inversely proportional to the preestimated load ratio, while driving the plasma display panel. The method comprises processing input video signals and measuring correlation of each frame with a preceding frame and regulating a speed at which the number of display-discharge pulses in a frame is controlled, depending on the correlation, i.e., regulating a rate of change of the number of display-discharge pulses per frame depending on the correlation.
The present invention provides an apparatus which controls the drive power of the plasma display panel in a driving apparatus of a plasma display panel. A load ratio preestimator preestimates a load ratio on a frame-by-frame basis, the load ratio being the ratio of the number of discharge cells to be display-discharged to the total number of discharge cells in the plasma display panel, a discharge number controller which controls a number of display-discharge pulses in a corresponding frame to be inversely proportional to the preestimated load ratio from the load ratio preestimator, a correlation number counter which processes input video signals and measures correlation of each frame with its preceding frame, and a control-timing regulator which controls the output timing of the discharge number controller according to the correlation from the correlation number counter and regulates a speed at which the number of display-discharge pulses in a frame is controlled. That is, the control-timing regulator regulates a rate of change of the number of display-discharge pulses per frame based on the correlation number.